1. Field of the Invention
The invention relates to telecommunication, and in particular to a method of scaling input data and a mobile device in a telecommunication system.
2. Description of the Related Art
In wireless communication, a transmitter such as a base station encodes and modulates transmitted data to transmit to a receiver through a transmission channel. The transmission typically is not continuous but manifests as “data bursts”, with one burst for each transmitted data block. The transmission channel, such as a radio frequency (RF) channel, distorts each data burst with a particular channel response, and further degrades each data burst with noise and interference. The receiver, such as a mobile phone, receives the data bursts, and processes every set of soft-decision bits therein to obtain a quantization output, referred to as soft-decision decoding.
Soft-decision decoding is beneficial in a receiver to provide higher receiver gain than would be possible with hard-decision, thereby combating common channel fading, interference and noise problems in the transmission channel. The receiver gain increases with soft-decision bits. Soft-decision decoding scales and quantizes each data burst with one or a few bits of precision to provide more than two states or levels. If data bursts are quantized to one-bit precision (<0V=1, ≧0V=0), the result is hard-decision data. If data bursts are quantized with more than one bit of precision, the result is soft-decision data, e.g., quantizing data bursts with three-bit precision results in 8 possible levels of quantization output. Before quantization each data burst is typically scaled by a single scale factor to provide proper amplitude for the quantization. Conventional scale factoring is based on a signal-to-noise-and-interference ratio (SINR) of the data burst.
However asynchronous communication systems such as Global System for Mobile communication (GSM) systems contain typically higher co-channel and adjacent channel interference. Further, since data is transmitted in bursts and not continuous, channel conditions of the transmission channel vary with time, resulting in changing interference and noise quantity, and varying SINR for each data burst.
Thus a need exists for a mobile device and a method of scaling data burst transmitted asynchronously through a channel under varying channel conditions.